Risk factors in multiple sclerosis: tuberculin reactivity, age at measles infection, tonsillectomy and appendectomy.

The purpose of the present study was to investigate whether risk of multiple sclerosis (MS) is associated with the occurrence of viral or bacterial diseases, with vaccinations, or with operative events during childhood. Our reference population was 198,000 persons recorded in the register of school health records from the Copenhagen council. We compared 92 MS patients contained in the register with matched controls from the register, three for each patients. Risk of MS was inversely associated with a positive tuberculin skin test at age 7 years, i.e. with exposure to tuberculosis before the age of 7, possibly also with the occurrence of measles infection before age 7 (not statistically significant). Disease risk was not significantly related to other viral or bacterial infections of childhood, nor to routine vaccinations, tonsillectomy, adenoidectomy or appendectomy. Our findings suggest a difference between MS patients and controls with respect to environment before school age, the former being less exposed to air-borne infections.